Electronically Excited States in Model Complexes of Noble Metal Clusters with Carbon Nanodots

Russian Physics Journal - Theoretical calculations of excited states in the complexes of gold and silver three-atom nanoclusters with carbon quantum nanodots are performed using the M062X...     

On a borderline between the NP-hard and polynomial-time solvable cases of the flow shop with job-dependent storage requirements

The paper is concerned with the two-machine flow shop, where each job requires an additional resource (referred to as storage space) from the start of its first operation till the end of its second operation. The storage requirement of a job is determined by the processing time of its first operation. At any point in time, the total consumption of this additional resource cannot exceed a given limit (referred to as the storage capacity). The goal is to minimise the makespan, i.e. to minimise the time needed for the completion of all jobs. This problem is NP-hard in the strong sense. The paper analyses how the parameter - a lower bound on the storage capacity specified in terms of the processing times, affects the computational complexity.

     

Synthesis of a disaccharide of phenolic glycolipid from Mycobacterium leprae (PGL-I) and its conjugates with bovine serum albumin

Russian Chemical Bulletin - Terminal disaccharide fragment of phenolic glycolipid from Mycobacterium leprae (PGL-I) was synthesized as a glycoside with 4-(2-aminoethoxy)phenyl aglycon. The obtained...     

Combined Quantum-Classical Simulation of Photoinduced Electronic Density Redistribution from Biopolymer Segments to Photochromic Probes

Russian Physics Journal - The mechanism of fluorescence quenching of the human serum albumin by transferring the energy of the photoinduced electronic excitation from the single tryptophan residue...     

Differences in reactivity of N-acetyl- and N,N-diacetylsialyl chlorides caused by their different supramolecular organization in solutions

O-Sialylation of a substituted indolin-3-one under phase-transfer catalysis conditions, which does not occur when N-acetylsialyl chloride is used, proceeds with N,N-diacetylsialyl chloride as the glycosyl donor. A study using dynamic light scattering of solutions of both sialyl chlorides under conditions close to the conditions used for glycosylation showed a difference in the correlation radii of light scattering particles in such solutions. This suggests that the introduction of an additional N-acetyl group into the sialyl chloride significantly alters the structure of the supramers of glycosyl donor, which apparently have an increased accessibility of individual molecules for the attack by a nucleophile, which increases its reactivity.

     

Are N-phthaloyl and O-allyl protective groups orthogonal?

Using allyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranoside as a model substrate, it was shown that the degree of orthogonality of N-phthaloyl and O-allyl protective groups under the conditions of hydrazinolysis of the phthalimide group depends on the amount of atmospheric oxygen in the reaction mixture during the reaction and during the work-up procedure.

     

Selectin Receptors 4: Synthesis of Tetrasaccharides Sialyl Lewis A and Sialyl Lewis X Containing A Spacer Group1,2

ABSTRACT

Synthesis of two isomeric tetrasaccharides, namely Neu5Acα(2→3)Galβ(1→3)[Fucα(1→4)GlcNAcβ (sLe^a) and Neu5Acα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ (sLe^x) as 3-aminopropyl glycosides is described. Preparation of these compounds was performed by sialylation of selectively protected trisaccharides Le^a and Le^x which contain three unsubstituted OH groups at positions 2, 3 and 4 of Gal residue. Glycosylation of Le^x trisaccharide with ethylthio sialoside under promotion by NIS and TfOH in acetonitrile was effective and regio- and stereoselective to give sLe^x derivative in 81% yield. In contrast, sialylation of the Lc^a acceptor was accompanied by a variety of undesirable by-processes, namely. N-thioethylation of the GlcNAc residue, β-sialylation, and lactonisation. In order to improve the yield of sLc^a tetrasaccharide the glycosylation of Le^a acceptor by sialyl donors of ethyl and phenyl thioglycoside (promoted by NIS-TfOH or NBS-Bu₄NBr), xanthate (promotion by NIS-TfOH mixture or MeOTf) and phosphite (promoted by TMSOTf) types was also studied. Among the reactions investigated the glycosylation by phenyl thioglycoside sialoside promoted by NIS-TfOH gives the best yield (39%) of sLe^a tetrasaccharide product.     

Influence of a cellulose diacetate matrix on the complexation kinetics of tetraphenylporphin with Zn and Cd

The dependence of the reaction rate of tetraphenylporphin zinc and cadmium complexes in a polymer matrix on a base of cellulose diacetate and low-molecular model solutions was investigated. The characteristics of the diffusive transport of aqueous solutions of zinc and cadmium acetates through the cellulose diacetate membrane were obtained. The kinetic control of the porphyrin reaction incorporated into the polymer, and the determining influence of the steric limitations of the matrix of a rigid chain polymer on macroheterocycle deformation (and thus its reactivity) are shown.